THE  ACTINIUM-URANIUM  RATIO  IN 
COLORADO  CARNOTITE 


KARL  H.  FUSSLER 


A  THESIS 

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THE   ACTINIUM-URANIUM  RATIO  IN 
COLORADO  CARNOTITE 


BY 


KARL   H.   FUSSLER 
/// 


A   THESIS 

Presented  to  the  Faculty  of  the  Graduate  School  of  the 

University  of  Pennsylvania  in  Partial  Fulfilment  of 

the  Requirements  for  the  Degree  of 

Doctor  of  Philosophy 


PRESS  OF 

THE  NEW  ERA  PRINTING  COMPANY 

LANCASTER,  PA. 


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7$.  I 


THE  ACTINIUM-URANIUM    RATIO   IN   COLORADO 
CARNOTITE. 


[Reprinted  from  The  Physical  Review,  N.  S.,  Vol.  IX,  No.  2,  February,  191 7. 


THE  ACTINIUM-URANIUM    RATIO   IN   COLORADO 
CARNOTITE. 

By  Karl  H.  Fussler. 

IT  is  generally  accepted  by  investigators  in  radio-activity  that  actinium 
is  a  branch  product  from  the  uranium  transformation  series.  This 
is  based  on  the  following  facts:  (i)  Actinium  is  always  found  in  uranium 
minerals;  (2)  Boltwood^  separated  the  actinium  from  North  Carolina 
uraninite  and  determined  the  ratio  of  its  activity,  with  its  products  in 
radio-active  equilibrium,  to  the  activity  of  the  uranium  with  which  it 
was  associated.  The  values  of  this  ratio,  from  the  four  determinations 
which  he  made,  were  0.14,  0.15,  0.24  and  0.36.  He  gives  the  value  0.28 
as  the  weighted  mean  of  these  results.  (3)  He^  also  measured  the  total 
activity  of  various  uranium  minerals  and  determined  what  fraction  of 
this  total  activity  is  due  to  each  of  the  separate  radio-elements  contained 
in  the  minerals.  His  results  indicate  that  the  activity  of  a  uranium 
mineral,  containing  equilibrium  amounts  of  the  various  radio-elements, 
is  about  4.7  times  the  activity  of  the -uranium  in  the  mineral.  The  sum 
of  the  activities  of  the  separate  radio-elements,  uranium  to  polonium, 
plus  0.28  X  uranium  for  the  actinium  series,  gives  4.64  X  uranium  as 
the  total  activity  of  the  mineral.  If  actinium  is  a  branch  product  of  the 
uranium  series  there  should  be  a  constant  ratio  between  the  activities 
of  the  actinium  and  of  the  uranium  in  all  uranium  minerals. 

Since  this  ratio  has  been  directly  measured  for  only  one  uranium 
mineral  and  for  only  two  specimens  of  that  mineraP  it  was  thought 
desirable  to  determine  it  using  another  uranium  mineral.  This  paper 
describes  the  experiments  carried  out  using  Colorado  carnotite. 

Through  the  courtesy  of  the  Cummings  Chemical  Company,  manu- 
facturers of  radium,  of  Lansdowne,  Pa.,  I  was  enabled  to  select  my 
specimens  from  ton  lots  of  mineral.  Only  large,  firm  lumps  of  the 
higher  grade  ores  were  chosen.  The  final  selection  was  made  at  the 
laboratory  from  the  bulk  of  the  mineral  brought  from  the  factory,  and, 
as  a  rule,  only  the  centers  of  the  larger  lumps  were  chosen.     The  two 

^  Boltwood,  Amer.  Jour.  Sci.,  XXV.,  p.  269,  1908. 

*  The  specimens  used  are  described  by  Boltwood  as  no.  3  and  no.  4  uraninite  from  Spruce 
Pine,  N.  C.  Two  of  the  results  were  obtained  from  one  sample  of  specimen  no.  3,  one  result 
from  another  sample  of  the  same  specimen,  and  one  from  a  sample  of  specimen  no.  4. 


No^2^-^']  COLORADO   CARNOTITE.  I43 

Specimens  finally  selected  represented  two  different  shipments  of  ore. 
Specimen  A  after  pulverizing  and  passing  through  a  40-mesh  screen 
consisted  of  about  300  grams  ©f  carnotite.  Specimen  B  was  a  lower 
grade  material.     There  were  about  75  grams  in  this  lot. 

The  radio-active  measurements  were  made  in  an  alpha-ray  electroscope 
which  will  not  be  described  as  it  differed  in  no  essential  detail  from  one 
described  by  Boltwood.^  The  gold-leaf  was  charged  by  connecting, 
through  a  water  resistance,  to  the  negative  terminal  of  a  400-volt  battery 
of  "Spindler  and  Hoyer"  cadmium  cells.  The  guard  ring  was  perma- 
nently connected  to  the  negative  terminal  of  the  battery.  The  case  of 
the  electroscope  and  the  positive  terminal  of  the  battery  were  connected 
to  earth. 

A  microscope,  with  a  graduated  scale  in  the  eye-piece,  was  rigidly 
clamped  in  front  of  the  electroscope.  The  readings  consisted  in  timing 
the  passage  of  the  tip  of  the  gold-leaf  over  a  certain  definite  portion  of 
the  graduated  scale.  The  sensitiveness  of  the  electroscope  was  deter- 
mined for  every  series  of  measurements  by  taking  a  reading  of  the  leak 
produced  by  a  standard  film  of  uranium  oxide.  This  standard  was 
made  several  years  ago  by  Professor  D.  H.  Kabakjian,  from  a  very  pure 
specimen  of  uranium  oxide.  It  was  deposited  in  the  form  of  a  thin  film 
on  a  light  brass  disc.  It  has  been  carefully  preserved  and  from  time  to 
time  its  activity  has  been  compared  with  the  activity  of  a  primary 
uranium  standard,  which  was  similarly  prepared,  and  which  has  been 
used  only  as  a  comparison  specimen  for  the  secondary  standards. 

The  natural  leak  of  the  electroscope  was  determined  for  every  series 
of  measurements  and  the  corrections  made  for  it.  It  was  fairly  low  and 
has  not  varied  materially  during  the  past  one  and  one  half  years. 

The  general  plan  of  the  experiments  was  to  separate  chemically  the 
ionium,  radio-actinium,  and  actinium,  as  a  group,  with  the  rare  earths 
as  oxalates,  from  the  other  radio-elements  in  a  specimen  of  carnotite, 
to  determine  the  weight  of  the  mixture  of  these  elements  and  the  non- 
radio-active  elements  separated  with  them  and  to  make  a  very  thin 
film,  of  known  weight,  on  a  metal  plate,  from  this  active  material.  The 
growth  of  activity  of  this  film  was  measured  at  intervals  over  a  period 
of  about  100  days,  at  which  time  the  equilibrium  value  had  been  attained. 
The  activity  due  to  ionium  and  actinium  plus  its  products  in  equilibrium 
in  one  gram  of  carnotite  was  calculated  from  the  equilibrium  value  of 
the  activity  of  this  film.  A  film,  of  known  weight,  was  also  made  from 
the  uranium  separated  from  the  same  specimen  of  mineral.  The  activity 
due  to  the  uranium  alone  in  one  gram  of  carnotite  was  calculated  from 

1  Loc.  cif.,  p.  272. 


144  KARL  H.   FUSSLER,  [j 


Second 
Series. 


the  activity  of  this  film.  Boltwood^  has  shown  that  the  activity  of 
ionium  in  a  uranium  mineral  is  34  per  cent,  of  the  activity  of  the  uranium 
with  which  it  is  associated.  This  result  was  used  in  calculating  the 
activity  of  the  ionium  per  gram  of  mineral.  Deducting  the  activity  due 
to  ionium,  from  the  combined  activity  of  ionium  and  the  actinium  series, 
gives  the  value  of  the  activity  due  to  actinium  and  its  products  in  equi- 
librium in  one  gram  of  the  mineral.  This  latter  value  divided  by  the 
activity  due  to  the  uranium  in  one  gram  of  the  mineral  gives  the  value 
of  the  actinium-uranium  activity  ratio. 

Because  of  the  minute  quantities  of  these  radio-elements  in  a  mineral 
the  usual  method  used  in  separating  them  is  to  introduce  into  the  solu- 
tions other  elements,  or  carriers,  which  are  either  isotopic,  or  chemically 
similar  to  them.  The  best  method  of  separating  ionium  from  a  mineral 
is  to  introduce  thorium,  if  not  already  present,  and  then  separate  the 
thorium  by  the  well-known  chemical  processes.  Wishing  to  avoid  the 
introduction  of  another  radio-element,  cerium  was  used  as  a  carrier, 
the  chemical  properties  of  which  are  not  very  different  from  those  of 
ionium.  In  the  same  way  lanthanum  was  used  as  a  carrier  for  the 
actinium.^  As  radio-actinium  is  isotopic  with  ionium,^  evidently  it  will 
be  precipitated  with  the  ionium.  The  details  of  the  experiments  are  as 
follows : 

Experiment  i. — Twenty-five  grams  of  specimen  A  carnotite  were  de- 
composed by  heating  with  dilute  nitric  acid  and  the  solution  evaporated 
to  dryness.  The  residue  was  treated  with  hot  dilute  nitric  acid.  The 
insoluble  matter  was  separated  by  decantation  and  again  treated  with 
the  hot  dilute  acid.  The  solutions  were  combined  and  the  insoluble 
matter,  consisting  largely  of  silica,  after  washing,  was  found  to  have 
negligible  activity.  The  solution  was  saturated  with  hydrogen  sulphide 
to  separate  the  insoluble  sulphides  after  the  addition  of  a  small  quantity 
of  bismuth  nitrate  to  ensure  complete  precipitation  of  the  polonium. 
The  filtrate  was  boiled  to  remove  the  excess  of  hydrogen  sulphide. 
Small  amounts  of  cerium  nitrate,  and  lanthanum  nitrate,  were  added, 
and  while  the  solution  was  still  hot,  an  excess  of  oxalic  acid  was  added 
and  allowed  to  stand  for  about  twenty  hours.  The  precipitated  oxalates 
were  removed,  a  minute  quantity  of  the  cerium  and  lanthanum  salts  was 
again  added,  and  the  precipitation  by  oxalic  acid  repeated.'^  The 
oxalates  were  combined,  converted  into  nitrates,  and  again  precipitated 

*  Loc.  cit.,  p.  289, 

2  Auer  von  Welsbach,  Sitzungber.  K.  Akad.  Wiss.  Wien,  1910,  119,  ii.,  a,  i. 
'  Fleck,  Journ.  Chem.  Soc,  103',  381,  1913. 

*  In  work  preliminary  to  these  experiments  it  was  found  that  a  third  oxalate  precipitate 
had  a  negligible  activity. 


}Jo^-2^^]  COLORADO   CARNOTITE.  1 45 

by  oxalic  acid.     The  oxalates  were  converted  into  oxides  by  intense 

ignition  over  the  blast-lamp.     The  rare  earth  oxides  obtained  in  this 

manner  weighed  1.0230  grams.      A  film  weighing  0.0082  gram  was  made. 

The  activity  of  this  film  when  it  had  reached  equilibrium,  was  5.202 

,.   .  .  .  1  •       .  1.0230 

divisions  per  minute.       This  gives  — — —  X  5.202  =  26  divisions 

25  X  0.0082 

per  minute  for  the  activity  due  to  the  ionium  and  the  actinium,  plus  its 

products  in  equilibrium,  in  one  gram  of  carnotite. 

The  filtrates,  from  which  the  oxalates  were  separated,  were  evaporated 
to  dryness  and  gently  heated  to  destroy  the  oxalic  acid.  The  residue 
was  taken  up  in  dilute  hydrochloric  acid,  a  small  amount  of  barium 
chloride  was  added,  and  the  radium  precipitated  as  sulphate  with  the 
barium.  The  addition  and  precipitation  of  the  barium  was  twice 
repeated  to  ensure  complete  removal  of  the  radium.  The  filtrate  was 
boiled  with  an  excess  of  sodium  carbonate,  containing  some  ammonium 
sulphide,  and  the  carbonates  filtered  off.  The  uranium  was  precipitated 
and  weighed  as  sodium  uranate.  It  weighed  6.6042  grams  and  the  film 
made  from  it  weighed  0.0096  gram.  The  activity  of  the  film  was  1.990 
divisions  per  minute.  This  gives  an  activity  of  55  divisions  per  minute 
for  the  uranium  in  one  gram  of  the  mineral. 

The  activity  of  the  ionium  per  one  gram  of  the  mineral,  using  Bolt- 
wood's  value,  should  be  (0.34  X  55)  18.6  divisions  per  minute.  De- 
ducting this  value  from  the  activity  calculated  from  the  ionium-actinium 
film  (26  divisions  per  minute  per  one  gram  of  mineral)  gives  7.4  divisions 
per  minute  as  the  activity  due  to  actinium  and  its  products  in  equilibrium. 
This  is  0.135  times  the  activity  of  the  uranium. 

Experiment  2. — Fifty  grams  of  specimen  B  carnotite  were  taken  for 
this  experiment.  The  material  was  treated  in  the  same  manner  as  that 
of  experiment  i.  The  activity  of  the  ionium-actinium  film  100  days 
after  separation  was  2.1 16  divisions  per  minute  which  gave  18.2  divisions 
per  minute  as  the  total  activity  of  the  ionium  and  actinium  per  one  gram 
of  mineral.  The  sodium  uranate  separated  weighed  8.5234  grams,  and 
the  film  weighed  0.0041  gram,  which  showed  an  activity  of  0.849  divi- 
sion per  minute.  This  gave  an  activity  of  35.2  divisions  per  minute 
for  the  uranium  in  one  gram  of  carnotite.  The  activity  of  the  ionium, 
calculated  as  before,  is  (0.34  X  35-3)  12.0  divisions  per  minute.  Sub- 
tracting this  from  the  combined  ionium-actinium  activity  gives  6.2 
divisions  per  minute  as  the  activity  of  the  actinium  series.  This  divided 
by  the  activity  of  the  uranium  (35.3  divisions  per  minute)  gives  0.176 
as  the  value  found  for  the  ratio  of  the  activity  of  the  actinium  and  its 
products  to  that  of  the  uranium  with  which  it  is  associated. 


146 


KARL   H.   FUSSLER. 


[Second 
[series. 


Experiment  J. — Twenty-five  grams  of  specimen  A  carnotite  were  treated 
in  the  same  manner  as  in  experiment  i.  The  activity  of  the  uranium 
per  gram  of  carnotite  was  51.5  divisions  per  minute.  The  combined 
activity  of  the  ionium  and  the  actinium  series  per  gram  of  carnotite 
was  23  divisions  per  minute.  The  calculated  activity  due  to  the  ionium 
(0.34  X  51-5)  is  17.5  divisions  per  minute  which  leaves  5.5  divisions  per 
minute  as  the  activity  due  to  actinium  and  its  products  in  equilibrium. 
This  divided  by  the  activity  of  the  uranium  gives  0.107  as  the  actinium- 
uranium  ratio. 

The  values  for  the  relative  activity  of  the  actinium  series  obtained  in 
these  experiments  were,  therefore,  0.135,  0.176,  and  0.107  X  Ur. 

A  theoretical  curve  was  plotted  on  the  assumption  that  an  equilibrium 
amount  of  radio-actinium  was  precipitated  with  the  actinium.  This 
curve  was  obtained  by  adding  the  ordinates  of  curves  I  and  //,  Fig.  i. 


• 

3 

'i 

> 

5  ^ 



X. 

^ 

^ 

2  60 

y^ 

9 

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y^ 

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u 

y^ 

y^^ 

^^ 

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y^ 

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y 

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• 

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y  ^ 

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^^"^-^5 

Ex^i»«.t  No.a 

10 

-- 

>   — 

To So — 30 ^ — : 

ro        <o        7«        eo      *« 

K 

DW 

Fig.  1. 

Curve  /  is  the  recovery  curve  of  actinium  freed  from  all  its  active  pro- 
ducts.^ The  ordinates  represent  the  activity  and  the  abscissae  the  time 
in  days  from  separation.  The  equilibrium  value  of  the  activity  is  taken 
as  100.  McCoy  and  Leman^  have  shown  that  the  equilibrium  activity 
of  radio-actinium  is  17.6  per  cent,  of  the  total  activity  of  the  actinium 
series.  This  value  is  used  as  the  initial  value  of  the  radio-actinium 
curve  (Curve  77).  The  crosses  give  the  experimental  values  of  the 
growth  with  time  of  the  activity  of  the  film  of  experiment  no.  2.  The 
curves  for  experiments  no.  i  and  no.  3  were  similar  in  shape,  but  with 
initial  activities  somewhat  lower.  (13.9  per  cent,  for  no.  i  and  11.7 
per  cent,  for  no.  3.)  The  agreement  is  well  within  the  limits  of  experi- 
mental error.     This,  I  believe,  indicates  that  the  film  did  not  contain 

1  Hahn,  Phil.  Mag.,  XIII.,  165.  1907- 
'  Phys.  Rev.,  4  Ser.  2,  1914,  p.  409. 


Na2!'^']  COLORADO  CARNOTITE.  1 47 

other  radio-active  elements  in  quantities  sufficient  to  appreciably  alter 
the  shape  of  the  actinium  plus  radio-actinium  curve.  The  disagree- 
ment between  the  experimental  and  the  theoretical  curves  may  be 
accounted  for  by  an  incomplete  precipitation  of  the  ionium  in  the  speci- 
mens. A  computation  shows  that  if  1.5  per  cent,  (for  film  of  experiment 
no.  2)  of  the  ionium  remained  in  the  solution  the  starting  point  of  the 
two  curves  would  agree.  This  would  make  the  actinium  ratio  larger  by 
about  2.8  per  cent. 

Conclusions. 

1 .  The  ratio  of  the  activity  of  the  actinium  series  to  the  activity  of  the 
uranium  associated  with  it  in  Colorado  carnotite  has  been  determined. 

2.  The  results  indicate  that  the  quantity  of  actinium  in  carnotite  is 
proportional  to  the  quantity  of  uranium. 

3.  The  value  of  the  ratio  is  of  the  same  order  of  magnitude,  but  some- 
what lower  than  that  obtained  by  Boltwood  using  North  Carolina 
uraninite. 

4.  The  results  are  in  agreement  with  the  theory  that  actinium  is  a 
branch  product  of  the  uranium  series. 

In  conclusion  I  wish  to  acknowledge  my  indebtedness  to  Professor 
Arthur  W.  Goodspeed  for  kindly  placing  at  my  disposal  all  the  facilities 
of  the  Randal  Morgan  Laboratory,  and  to  Professor  D.  H.  Kabakjian 
for  suggesting  the  subject  of  this  research  and  for  his  continued  co- 
operation and  valuable  criticisms  during  the  course  of  the  investigation. 

Randal  Morgan  Laboratory  of  Physics, 
University  of  Pennsylvania. 


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